Criticism and the Growth of Knowledge
How science knows what's true
Description
In July 1965, a few hundred philosophers, physicists and historians gathered at Bedford College in London for what was billed as the International Colloquium in the Philosophy of Science. The headline event was a session pitting Karl Popper against Thomas Kuhn — two men who had, in different ways, become the reigning accounts of how science actually works. Popper thought science advanced by ruthless testing: a theory was scientific only if it could be proven wrong, and every real experiment was an attempt at execution. Kuhn thought science mostly did no such thing. It settled into long stretches of routine puzzle-solving inside a shared framework, and only occasionally, in a kind of collective conversion, threw the framework out.
The clash didn't resolve on the day. It spilled into years of written exchange, and in 1970 Imre Lakatos and Alan Musgrave gathered the whole quarrel into a single volume — Popper, Kuhn, the young Lakatos, Paul Feyerabend, John Watkins, Stephen Toulmin and others, arguing past and occasionally into each other. The book became one of the most-read texts in twentieth-century philosophy of science, partly because the fight was real. What looked like a technical squabble about method was really a fight over something bigger: whether we can say, with any authority, that today's science knows more than yesterday's.
That is the uncomfortable thing the book circles. We tend to assume science is the one human activity that reliably gets closer to the truth. But when you ask what makes it rational — what separates a genuine advance from a fashion, a stubborn defense from an honest one — the confident answers start to wobble. Everyone in the room believed science was special. Almost nobody agreed on why.
The question we’re asking : When science changes its mind, is it following a rule — or just following the crowd?What we’ll see : A famous London confrontation, and the rival accounts of scientific progress it forced three sharp thinkers to defend.
Table of contents
01Chapter 1 — A conference that turned into a duel
The setup looked collegial. Popper was the senior figure, an Austrian émigré who had reshaped the field with his 1934 Logic of Scientific Discovery and become, by the 1960s, the establishment view of what made science science. Kuhn was the insurgent, a physicist-turned-historian whose 1962 book, The Structure of Scientific Revolutions, had sold in numbers philosophy books almost never reach. The organizers expected a meeting of minds. What they got was closer to two people describing different animals and insisting it was the same one.
The disagreement was not about facts. Both men knew the history of physics cold; both could recite the same episodes — Copernicus, Newton, Einstein. The split was about what those episodes meant. For Popper, the story of science was a story of conjectures boldly made and bravely exposed to refutation. A scientist worthy of the name went looking for the experiment that could sink their own theory. Dogma was the enemy; criticism was the engine.
02Chapter 2 — Popper's clean rule and its embarrassing cracks
Popper's appeal is that his rule is clean. A theory earns the label scientific by sticking its neck out — by forbidding certain outcomes, by saying what cannot happen. Einstein's general relativity predicted that starlight would bend by a specific amount as it passed the sun; had the 1919 eclipse measurements come back different, the theory was finished. That risk, for Popper, was the mark of respectability. By contrast, theories that explained everything — he had Freudian psychoanalysis and Marxist history in mind — explained nothing, because no conceivable observation could count against them. Falsifiability was the line between science and pretenders.
It is a bracing idea, and the trouble showed up almost immediately when you asked how it works in practice. No theory is ever tested alone. When an experiment goes wrong, the scientist faces a choice: abandon the grand theory, or blame one of the dozens of background assumptions — the calibration of the instrument, the purity of the sample, an auxiliary hypothesis nobody had bothered to state. History is full of cases where a stubborn anomaly turned out to be a fault in the equipment, not the theory. If a single failed prediction were really a death sentence, science would have executed most of its best ideas in infancy.
03Chapter 3 — Kuhn's paradigms and the fear of the mob
Kuhn's alternative was built around a word that escaped into common speech and never came back: paradigm. A paradigm, in his richest sense, is not just a theory but a whole package — the shared assumptions, the standard problems, the exemplary solutions students learn to imitate, the tacit sense of what a good question even looks like. Normal science happens inside a paradigm. It runs smoothly until anomalies pile up faster than they can be absorbed, confidence erodes, and the field enters crisis. Then, sometimes, a new paradigm arrives and the community switches — not gradually, but in something like a gestalt flip.
The disturbing part, for Popper and his allies, was Kuhn's claim that rival paradigms are incommensurable. Because each frames the questions, the standards, even the meaning of key terms differently, there is no neutral scoreboard on which to declare the winner. Choosing a new paradigm, Kuhn suggested, has more in common with a conversion than with a calculation. To Popper's camp this sounded like surrender. If theory choice can't be settled by evidence and argument, what is it settled by? The suspicion, voiced sharply in the volume, was that Kuhn had handed the decision over to the crowd — to whatever the scientific community happened to agree on.
04Chapter 4 — Lakatos and the long game of research programmes
Lakatos, still in his forties and sharpening his knives, saw the whole quarrel as a trap with two bad exits. Take Popper strictly and science becomes impossibly heroic, killing theories at the first bad result. Take Kuhn and rationality dissolves into crowd psychology, a matter of who converts whom. Lakatos wanted to keep Popper's insistence that science is answerable to something beyond fashion, while admitting Kuhn's obvious point that scientists cling to good theories through rough patches — and are right to.
His move was to change the unit under evaluation. Don't judge a single theory against a single experiment, he argued. Judge a research programme — a long-running project with a hard core of central assumptions that its practitioners agree not to question, surrounded by a protective belt of adjustable hypotheses that soak up the anomalies. Newtonian mechanics, evolutionary biology, and the like are programmes, not lone claims. And this reframes the real question: not is it true today, but is it going somewhere?
05Conclusion
The London confrontation never produced a winner, and the volume that captured it does not pretend otherwise. Popper kept his conviction that criticism is the soul of science and dogma its enemy. Kuhn kept his historian's insistence that science mostly runs on shared, unquestioned frameworks and lurches forward in rare upheavals. Lakatos threaded between them with his research programmes, and Feyerabend cheerfully torched the whole idea that any rule governs the game. What united the arguers was a refusal to say that science is just one belief system among others — and a shared inability to state, cleanly and finally, what makes it more.
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